1. Field of the Invention
This invention generally relates to a bicycle rear derailleur. More specifically, the present invention relates to a bicycle rear derailleur having a movable chain guard member.
2. Background Information
Bicycling is becoming an increasingly more popular form of recreation as well as a means of transportation. Moreover, bicycling has become a very popular competitive sport for both amateurs and professionals. Whether the bicycle is used for recreation, transportation or competition, the bicycle industry is constantly improving the various components of the bicycle. One component that has been extensively redesigned is the bicycle rear derailleur.
Typically, a rear derailleur has a base member and a movable member with a chain guide movably coupled to the base member via a linkage assembly. The base member is attached to the frame of the bicycle. The chain guide is configured to move the chain laterally over a plurality of rear sprockets. A spring biases the chain guide to an innermost or outermost position relative to the rear sprockets. A bowden-type control cable is typically coupled to the rear derailleur and to a conventional shift control device in order to control movement of the chain guide. The chain guide can be moved laterally by moving the linkage assembly via the inner wire of the control cable. Pulling the inner wire moves the chain guide against the biasing force of the spring, while releasing the inner wire causes the chain guide to move due to the biasing force of the spring.
Usually, the base member of a typical rear derailleur is mounted in a stationary position during normal use. However, the base member can typically be rotated against the biasing force of an internal spring and/or against the force of chain tension in order to move the derailleur out of the way for removal of the rear wheel. While this base member arrangement works relatively well, an individual (rider, mechanic, etc.) must hold the rear derailleur out of the way during removal of the rear wheel. This can be difficult, cumbersome and/or inconvenient depending on the individual and the bicycle.
The most common chain guide includes a pair of pulleys mounted between a pair of parallel plates so that the pulleys are movable about a common pivot axis in response to changes in chain tension. However, in recent years, rear derailleurs have been provided in which the chain cage that supports the tension pulley may interfere with the guide pulley and/or the chain cage that supports the guide pulley in certain gear orientations. Also, interference between parts of the chain guide and the chain may occur in certain gear orientations. Furthermore, the chain cage that supports the guide pulley may interfere with the rear sprockets during removal of the rear wheel.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved bicycle rear derailleur. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.